Sound picture fader



y 4, 1939- w. L. DOUDEN 2,164,736

10 v fi/Fmy II 9 I? 7 :9- 3 -(IMIIIIIF A INVENTOR ATTORNEY July 4, 1939.

w. L. DOUDEN SOUND P ICTURE FADER Filed Feb.

2 Sheets-Sheet 2.

INVENTOR BY 7% 24M ATTORNEY Patented July 4, 1939 UNITED STATES PATENTOFFICE SOUND PICTURE FADER Delaware Application February 9, 1935, SerialNo. 5,876

12 Claims.

This invention relates to sound faders suitable for use in connectionwith sound pictures and the like, and has for its principal object theprovision of an improved apparatus and method of operation wherebycurrent may be readily switched from the exciter lamp of one sound headto that of another without producing undesired noise in the loudspeakerwith which the sound heads are associated.

The various types of sound faders provided in the past have not beenaltogether satisfactory for the reason that they are unduly complicatedand expensive or can not be operated without the production of click orother extraneous noise when the circuit is switched from one excitedlamp to another. In accordance with this invention, this difiiculty isavoided by providing between the control switch and the exciter lamp adelay circuit which produces a more or less gradual decrease in thecurrent of the going-out lamp and a more or less gradual increase in thecurrent of the coming-in lamp. As hereinafter explained, the delaycircuit or network may include as one of its elements the field coil ofthe loudspeaker which forms a part of the sound reproducing apparatusand is readily applicable to difierent types of exciter lampenergization systems.

The invention will be better understood from the following descriptionwhen considered in connection with the accompanying drawings, and itsscope will be pointed out in the appended claims.

Referring to the drawings:

Figs. 1, 2 and 3 illustrate sound faders which include difierentarrangements of the delay network elements, and

Fig. 4 illustrates a combination of a combined delay network andoscillation generator for controlling the exciter current.

The arrangement of Fig. 1 includes exciter lamps Ill and II connected tobe energized from a current source I2 through leads I3 and I4respectively. Interposed between these two sets of leads is the fieldcoil I5 of a loudpeaker I6. The connections of the circuits arecontrolled by a switch IT.

A condenser I8 is connected across the terminals of the lamp I0 and acondenser I9 is connected across the terminals of the lamp I I.

With the switch I! in its illustrated position, the lamp II isshort-circuited and the lamp II] is supplied with current from thesource I2 through the loudspeaker field coil I5 and the leads I3. Underthese conditions, of course, the lamp II is dark. When it is desired tolight the lamp II the switch I! is moved to its left hand operatingposition. This movement of the switch first opens the short-circuit onthe lamp I I thus charging the condenser I9 at a sub-normal voltage andgradu ally building up the current of the lamp II through theloudspeaker field coil I5 and the lamp Ill and permitting the condenserI8 to discharge due to the reduced voltage applied to the lamp 19.Further movement of the switch I! short-circuits the lamp II) thusincreasing the voltage applied to the condenser I9 of the lamp II, therate at which the current of the lamp II is increased being delayedsomewhat by charging of the condenser I9 and speaker coil I5.

The arrangement of Fig. 2 differs from that of 15 Fig. 1 in that thereis added to each of the delay networks a series inductance and anadditional shunt condenser. This modified net-work produces a somewhatslower rate of exciter lamp current change than that illustrated byFig. 1. It 20 is controlled by a switch 2!! movable to connect eithercircuit with the source I2.

The arrangement of Fig. 3 is similar to that of Fig. 1 except that theloudspeaker field coil I5 is replaced by choke coil 2|. 25

Fig. 4 illustrates the application of the invention to an exciter lampsystem wherein the excitation current is delivered at an inaudiblefrequency. As in the case of Fig. 2, a filter comprising a seriesinductance and a pair of shunt capacities are arranged to be interposedby a switch 20 between the exciting lamps and the current source I2.Interposed between each delay circuit or filter and its correspondingexciter lamp is an oscillation generator 22 or 23 adapted to delivercurrent at an inaudible frequency depending on its tuning. Light fromthe exciter lamp I0 is transmitted to a photocell 24 through an opticalsystem 25 and a sound record 26. Similarly, light from the exciter lampII is transmitted to a photocell 40 27 through an optical system 28 anda sound record 29.

This latter form of the invention is particularly effective. Since thefiltering is accomplished in the plate circuit of the oscillator tube,the filter unit is acting on a small current at a high voltage and avery efiicient filter can be used which is neither bulky nor expensive.If the filter of the other forms of the invention is used with thecustomary exciter lamps operating with a rather heavy current at a lowvoltage, the size of the condensers and inductances must of course beincreased accordingly.

It will be apparent from the foregoing that I have provided an improvediader which avoids clicks or thumps in the sound reproducing deviceduring the change-over and that the device of my invention is also freefrom the noises and other difiiculties inherent in the prior art deviceshaving moving contacts as in rheostats, fading potentiometers and thelike. Further, my device can be made in the form of a single unit whichhas no moving parts and is adapted to be installed in any usual soundpicture system.

Attention is called to the fact that the system of this invention is notlimited to the illustrated embodiments but is readily applicable todifferent types of illuminating circuits and to any desired number oflight sources.

I claim:

1. Sound reproducing apparatus including a plurality of exciter lamps,power supply leads, means for controlling the rate at which said lampsare energized and de-energized, and circuit control means foroperatively associating said lamps with said leads one after the other.

2. A sound reproducing apparatus including a plurality of light sources,power supply leads, circuit control means for operatively associatingsaid sources with said leads one after the other, and means forcontrolling the rate at which said sources are energized andde-energized.

3. Sound reproducing apparatus including a loudspeaker, a plurality ofexciter lamps, power supply leads, current delay means including thefield coil of said speaker for controlling the rate which said lamps areenergized and de-energized, and circuit control means for operativelyassociating said lamps with said leads one after the other.

i. The method of energizing and deenergizing the exciter lamps of asound reproducer including a loudspeaker which includes connecting thefield coil of said speaker in series with said lamps, andshort-circuiting one of said lamps.

5. A sound reproducing apparatus including a plurality of exciter lamps,power supply leads, current delay means, oscillator generator means, andcircuit control means for alternatively connecting said leads to saidlamps through said circuit delay and oscillation generator means.

6. An illumination system including a plurality of light sourcesarranged to be energized one after the other, power supply leads,current delay means for controlling the rate at which said sources areenergized and de-energized, and circuit control means for alternativelyconnecting said sources to said leads.

'7. Sound reproducing apparatus including a plurality of exciter lamps,power supply leads, means for controlling the rate of increase ordecrease of current through said lamps when they are energized andde-energized, and circuit control means for operatively associating saidlamps with said leads one after the other.

8. A sound reproducing apparatus including a plurality of light sources,power supply leads, circuit control means for operatively associatingsaid sources with said leads one after the other, and means forcontrolling the rate at which the current increases or decreases throughsaid sources when they are energized and de-energized.

9. Sound reproducing apparatus including a loudspeaker, a plurality ofexciter lamps, power supply leads, current delay means including thefield coil of said speaker for controlling the rate at which the currentincreases or decreases when said lamps are energized and de-energized,and circuit control means for operatively associating said lamps withsaid leads one after the other.

10. An illumination system including a plurality of light sourcesarranged to be energized one after the other, power supply leads,current delay means for controlling the rate at which the currentthrough said sources increases or decreases, when said sources areenergized and deenergized, and circuit control means for alternativelyconnecting said sources to said leads.

11. Photophonographic apparatus including two exciter lamps connected inseries, means providing sufiicient current and voltage for one of saidexciter lamps, and means for short circuiting one of said exciter lamps.

i2. Photophonographic apparatus including a plurality of exciter lampsconnected in series, means for selectively short circuiting said eXciterlamps, and fixed means for controlling the rate of change of temperatureof said eXciter lamps.

WILLIAM L. DOUDEN.

